The invention relates to improvements in apparatus for severing running webs of paper, foil or like flexible materials, and more particularly to improvements in apparatus which can be utilized with advantage to subdivide running webs of flexible material into narrower webs or strips. Still more particularly, the invention relates to improvements in apparatus of the type disclosed in commonly owned U.S. Pat. No. 4,257,299 granted Mar. 24, 1981 to Kurt Aykut for "Means for moving a rotary knife in apparatus for cutting paper sheets or the like".
The apparatus which is disclosed in the patent to Aykut employs an upright rod-like guide which carries a holder for a first rotary knife. A driven second rotary knife is installed at a level beneath the first knife, and the first knife and its holder are movable with reference to the guide in parallelism with the axis of the second knife. Such adjustability of the first knife relative to the second knife renders it possible to select the extent of overlap between the two knives as well as the distance between the planes of the cutting edges of the knives.
A drawback of presently known apparatus of the above outlined character is that unavoidable clearances and/or clearances which develop as a result of progressing wear unduly affect the accuracy of positioning of the knives relative to each other. Vibrations of the knives in actual use of heretofore known apparatus also contribute to changes in orientation and can affect the quality of the cutting action and the useful life of the knives as well as the life expectancy of the entire severing apparatus. For example, vibrations can cause a change of orientation of the first knife relative to the second knife, and such change of orientation becomes more pronounced in response to progressing wear upon the means for holding, moving and adjusting the first knife.